Abstract
The choice of driving a heat pump with an electrically- or a thermally-driven
engine is a vexing question complicated by the carbon footprint and environmental
impact of using electricity versus natural gas (or waste heat) as the main
driver for the respective engines. The amount of useful work generated by these
two distinct engines is the focal point of this paper, which addresses a key question:
which engine presents a better choice for a given heat pumping application
within the constraints of energy and environmental stewardship? Extensive use
of energy, exergy, and availability analysis is necessary to quantify the useful
work and to examine the issue holistically for both types of engines. The
methodology explains why the output of work from these two distinct engines
to satisfy a given load is vastly di erent, a direct consequence of their inherent
Irreversibility. Thermodynamic consistency is guaranteed by satisfaction of the
First and Second Laws applied to closed systems and their subsystems. The general
conclusion is that thermally-driven engines are not industrious converters of heat to mechanical work.
